Will all good deeds be useless if one trangresses the sacred limits of Allah in private according to this Hadith?

I need help with this hadith of [Sunan Ibn Majah 4245](https://www.sunnah.com/urn/1343850) : >“I certainly know people of my nation who will come on the Day of Resurrection with good deeds like the mountains of Tihamah, but Allah will make them like scattered dust.” Thawban said: “O Messenger of Allah, describe them to us and tell us more, so that we will not become of them unknowingly.” He said: “They are your brothers and from your race, worshipping at night as you do, but they will be people who, when they are alone, transgress the sacred limits of Allah.” Will the deeds be rendered useless ONLY when one doesn't repent and dies in that state? Are the deeds still valid as long as one doesn't die not repenting beforehand?